Research progress on the water-carbon coupling processes at different scales in karst regions

ZHANG Jianchun; ZHU Jiang; HE Changde; JIA Zhi; ZHU Lifei; YI Yin; GONG Jiyi

doi:10.11932/karst20250205

Abstract：Karst regions are characterized by exposed bedrock,poor soils,and severe soil erosion,leading to a fragile and sensitive ecological environment,making them a key region for global environmental change research.The water cycle and carbon cycle are two key processes within ecosystems.The water cycle serves as a crucial material foundation for maintaining ecosystem stability and acts as an important vehicle for material circulation.In contrast,the carbon cycle represents a significant aspect of energy flow and material circulation.The interplay between these cycles is vital for sustaining ecosystem functions and environmental effects.In karst regions,the hydrological processes are complex,and the ecological environment is vulnerable.The water-carbon coupling is affected by natural and human factors,hence,studying the coupling process of karst region is essential for exploring the ecosystem in this area.Although considerable researches have been conducted on water-carbon coupling processes in karst areas,there remains a lack of systematic induction and summary of existing scientific findings,and future research directions need to be clearly guided and sorted.Thus,a comprehensive review and analysis of the water-carbon coupling processes in karst regions is particularly necessary. This study firstly starts from different spatial scales,from the leaf-scale level to the regional-scale level,to reveal the coupling mechanism between the water cycle and the carbon cycle.Combining the topographical and geomorphic characteristics of karst areas,the regional water-carbon coupling research of which is expanded from the Soil-Plant-Atmosphere-Continuum(SPAC)to the Soil-Rock-Plant-Atmosphere-Continuum(SRPAC).The Water Use Efficiency(WUE)is a key indicator for measuring water-carbon exchange,which is affected by the factors such as unique topography,vegetation,and etc.,showing significant differences from the non-karst areas.At the leaf-scale,stomatal behavior regulates photosynthesis and transpiration,affectingthe plant's water-use strategy.At the plant scale,the water-carbon utilization of vegetation exhibits topographic variations,with WUE being constrained by factors such as soil moisture.At the ecosystem scale,water-carbon coupling correlates with hydro-thermal environment and CO2 concentrations,whilethe groundwater circulationdrives the carbon cycling process.At the regional scale,water-carbon coupling manifests through the relationship between vegetation carbon sequestration and runoff generation and confluence,showing the exploration of the spatial-temporal distribution of WUE is of great significance for rocky desertification control. Secondly,an analysis is carried out from multiple perspectives such as climate change,vegetation restoration,land-use change,and engineering measures to summarize the impacts of natural and human activities on the water-carbon coupling processes.Climate change leads to fluctuations in precipitation patterns and temperature,directly altering the path and intensity of the water cycle,and thus affecting the carbon cycle.Vegetation restoration indirectly affects water-carbon coupling by regulating the regional climate and hydrology through soil and water conservation by roots and increasing vegetation coverage.Land-use change profoundly affects the water-carbon cycle process by influencing the carbon cycle and water resource distribution through changes in soil and runoff.Various engineering measures,such as the construction of water conservancy facilities,soil-water conservation projects,and tunnel construction,also have a significant impact on water-carbon coupling processes. Finally,potential future research hot spots are sorted out and extended classification methods of water-carbon coupling in combination with the karst geological background are proposed in this paper.It is suggested that a comprehensive monitoring system should be established,various carbon sink studies be integrated,and an interdisciplinary approach be adopted to carry out the simulation and prediction research on water-carbon coupling process in karst areas..The water-carbon coupling model should be improved,and the spatial-temporal resolution of data should be enhanced.In-depth research on the impacts of climate change and various human activities on the water-carbon coupling process in karst areas should be conducted in multiple directions.This study provides a new perspective for future research on water-carbon balance in karst areas and shows positive significances for the scientific formulation of water resource and carbon balance management policies in karst regions.